This dataset contains long-term (2021–2023), high-frequency time series of dissolved gas concentrations—specifically CH₄, CO₂, H₂, N₂, O₂, Ar, He, and Kr—measured in deep alpine groundwater at **Lavey-les-Bains**, Switzerland. Measurements were acquired using a portable membrane-inlet mass spectrometer (**miniRUEDI**) and calibrated with certified gas standards to ensure high analytical precision. The time series span multiple seasonal cycles and are used to investigate how seasonal hydrological fluctuations influence microbial community structure in deep aquifers. These data underpin a peer-reviewed study that demonstrates a decoupling between dynamic geochemical conditions and the stability of microbial communities at depth. The repository includes: * Readme.md file. * Raw and cleaned gas measurement files from two deep thermal wells. * Scripts for processing, normalization, and seasonal analysis. ## Peer-Reviewed Article *Resilience of deep aquifer microbial communities to seasonal hydrological fluctuations* Authors: Sébastien Giroud, Longhui Deng, Mark A. Lever, Oliver S. Schilling, Rolf Kipfer DOI: https://doi.org/10.1073/pnas.2422608122